Low energy method of preparing basic metal carbonates and other salts

ABSTRACT

A method of preparing basic metal carbonate selected from the group consisting of zinc carbonate, nickel carbonate, silver carbonate, cobalt carbonate, tin carbonate, lead carbonate, manganese carbonate, lithium carbonate, sodium carbonate, and potassium carbonate from metals comprising: contacting the metal with an aqueous solution comprising an amine, carbonic acid, and oxygen under conditions where the metal is converted into basic metal carbonate; and recovering the basic metal carbonate.

BACKGROUND OF THE INVENTION

Basic metal carbonates (BMC) are well-known chemical compounds whichhave a variety of uses including, without limitation, in pigments,chemical manufacturing, petroleum refining, electronics, andpharmaceuticals. Generally, BMC may be represented by the followingformulae: (M₂CO₃)_(x)(MOH)_(y), (MCO₃)_(x)(M(OH)₂)_(y),(M₂(CO₃)₃)_(x)(M(OH)₃)_(y), or (M(CO₃)₂)_(x)(M(OH)₄)_(y), wherein x>0and y>0, and wherein the valency of the metal ion is 1, 2, 3, or 4,respectively. Examples of BMC formulae for specific metals include:zinc, (ZnCO₃)_(x)(Zn(OH)₂)_(y); nickel, (NiCO₃)_(x)(Ni(OH)₂)_(y); andsilver, (Ag₂CO₃)_(x)(AgOH)_(y).

Methods for the preparation of a variety of BMC are known in the art.U.S. Pat. No. 6,555,075 describes a method in which basic zinc carbonate(BZC) is formed from an aqueous solution of zinc ash and urea. Thisprocess requires multiple steps of dissolution and precipitation andsubstantial energy input to drive off impurities and improve yields.U.S. Pat. No. 5,281,494 discloses a method of producing nickelhydroxide/basic nickel carbonate of varying CO₃ content from aqueoussolutions of nickel powder, oxygen and ammonia by using carbonate ion ascatalyst. This process also requires elevated temperatures. Anothergeneral method for preparing BMC is by electrolytic oxidation of metalin aqueous solution of carbonate, such as the process disclosed in U.S.Pat. No. 6,183,621 for producing basic cobalt carbonate.

A method for preparing BMC which provides advantages over known methodswould be desirable. The biggest advantage of the present method is thatthe energy required to make these salts is much less than in othermethods. We have shown that the present method works with zinc, nickel,silver, and cobalt as the metal cation component. The method should workas well for other metals, including tin, lead, manganese, and others. Itis also within normal reason to expect that the carbonate anion could bereplaced with other anions, including nitrates, sulfates, andphosphates.

BRIEF SUMMARY OF THE INVENTION

The present invention meets the foregoing and other needs by providing,in one aspect, a method of preparing BMC selected from the groupconsisting of zinc carbonate, nickel carbonate, silver carbonate, cobaltcarbonate, tin carbonate, lead carbonate, manganese carbonate, lithiumcarbonate, sodium carbonate, and potassium carbonate from metalscomprising: contacting the metal with an aqueous solution comprising: anamine; carbonic acid; and oxygen, under conditions where the metal isconverted into basic metal carbonate; and recovering the basic metalcarbonate, wherein the metal is selected from the group consisting ofzinc, nickel, silver, cobalt, tin, lead, manganese, lithium, sodium, andpotassium.

A further aspect of the invention provides, a continuous method ofpreparing basic metal carbonates selected from the group consisting ofzinc carbonate, nickel carbonate, silver carbonate, cobalt carbonate,tin carbonate, lead carbonate, manganese carbonate, lithium carbonate,sodium carbonate, and potassium carbonate from metals comprising: (a)providing an aqueous solution of ionized metal, the aqueous solutioncomprising an ionized metal, an amine, carbonic acid, and water in areaction vessel; (b) adjusting the pH of the solution until basic metalcarbonate is formed; (c) recovering the basic metal carbonate from theaqueous solution by subjecting the aqueous solution to filtration; (d)transferring the aqueous solution which remains after the recovery ofbasic metal carbonate in step (c) into a second vessel; (e) removingcarbon dioxide from the aqueous solution which remains after therecovery of basic metal carbonate in step (c); (f) introducing ametal-containing material into the aqueous solution which remains afterthe removal of carbon dioxide in step (e); (g) oxidizing themetal-containing material to provide a replenished ionized metalsolution; and (h) introducing the replenished ionized metal solutioninto the reaction vessel, wherein the metal is selected from the groupconsisting of zinc, nickel, silver, cobalt, tin, lead, manganese,lithium, sodium and potassium.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram showing an exemplary operational flow of acontinuous method of preparing a basic metal carbonate according to oneaspect of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The various aspects of the present invention provide methods forpreparing BMC.

In one aspect, the invention provides a method of preparing BMC selectedfrom the group consisting of zinc carbonate, nickel carbonate, silvercarbonate, cobalt carbonate, tin carbonate, lead carbonate, manganesecarbonate, lithium carbonate, sodium carbonate, and potassium carbonatefrom metals comprising: providing a solution of metal in a reactionvessel, the solution comprising metal, an amine, carbonic acid, oxygenand water, adjusting the pH of the solution until BMC is provided; andrecovering the BMC, wherein the metal is selected from the groupconsisting of zinc, nickel, silver, cobalt, tin, lead, manganese,lithium, sodium, and potassium.

The foregoing method may be practiced in any suitable reaction vessel,e.g., a spray chamber, a stirred tank reactor, a rotating tube reactor,or a pipeline reactor, in either a continuous or batch process. It isdesirable to practice the method as a continuous process, more desirablyusing a continuous stirred tank reactor.

The particle size of BMC may be controlled by varying the concentrationsof metal and ammonia in the solution, as well as by regulating the inputrate of metal solution and/or CO₂ into the reaction vessel, and/or theendpoint of the precipitation reaction. The particle size may also becontrolled by other process parameters, such as residence time ortemperature.

In the solution provided in the reaction vessel, or feed solution, themetal included therein may originate from any suitable source. Inaddition to #1 metals (99% metal of interest) which may include metaltubing, powders, flakes, shavings, wires, and the like, suitablemetal-containing material may be metal-containing plastics, alloys,clads, or compounds.

In practice, a typical metal-containing feed stream contains ammonia,water, carbonic acid, oxygen, and other components. A typical feedstream will include components, in certain amounts, as follows: metal,from about 10 g/L to about 160 g/L, desirably from about 20 g/L to about85 g/L; water; oxygen; ammonia, from about 3 g/L to about 110 g/L,desirably from about 50 g/L to about 90 g/L, and ammonia to metal molarratio from about 0.5:1 to about 8:1, desirably from about 1.5:1 to about7:1, depending on the metal involved; and carbonic acid from about 15g/L to about 130 g/L, desirably from about 70 g/L to about 110 g/L.

Generally, as the content of the feed stream is known, one skilled inthe art should be able to create the feed stream with the amount of eachcomponent needed to be present in the reaction vessel to practice theinventive methods.

In the aspect of the invention that involves introducing ametal-containing material into a metal-depleted solvent system toprovide an enriched metal solution, an additional amount of an amine maybe added to assist in solubilizing the metal in the aqueous medium. Theamine is desirably ammonia (which exists in the aqueous medium inequilibrium with ammonium hydroxide). The amount required to effect thisdissolution will vary, but will generally range from about 0.5:1 toabout 8:1, and desirably from about 1.5:1 to about 7:1, moles of amineto moles of metal. On an absolute basis, the amount of amine in theaqueous solution is desirably limited, ranging from about 3 g/L to about110 g/L, and more desirably from about 50 g/L to about 90 g/L, of NH₃.In general, as the pressure in the reactor vessel increases, theallowable amine concentration may be increased.

The carbonic acid may be provided in the reaction vessel by any suitablemeans, but is preferably provided by introducing CO₂ into the reactionvessel, e.g., by bubbling CO₂ through the aqueous solution, or byproviding a relative increase in the partial pressure of CO₂ within thereaction vessel. As used herein, the term carbonic acid includescarbonic acid as well as bicarbonate and carbonate ions, as it will beappreciated by one of ordinary skill in reading this disclosure that allof these species may be present when CO₂ is introduced into the aqueoussolution.

Following precipitation and separation of the solids, it may benecessary to reduce the carbonate level, or increase the pH, in thesolution to provide a suitable solution for metal leaching. This can beaccomplished by reducing the partial pressure of CO₂ in the vessel, ornominally through a reduction of the total pressure within the reactionvessel.

The relationship between the components in the system, while not beingbound by theory, may be simplistically explained in terms of anequation: [M^(x+)]^(n)[OH⁻]^(m)[CO₃ ²⁻]^(p)=K_(sp), wherein x, n, m, andp are greater than 0, and K_(sp) is a solubility product for BMC. Whenthe products of certain ionic concentrations exceed the solubilityconstant for BMC (i.e., K_(sp)), BMC will precipitate out of thesolution. Not shown in the K_(sp) equation is the solvating ligandammonia that influences the concentration of metal ions available forbonding.

In the inventive methods, selectively increasing the concentration ofone or more of metal ions, hydroxide ions or carbonate ions, ordecreasing the ammonia concentration may be sufficient to cause BMC toprecipitate from the solution.

For this invention addition of the CO₂ also adjusts the pH of thesolution in order to precipitate BMC. In this regard, the pH of thesolution is desirably relatively low, for example less than about 10,during the formation of BMC. More desirably, the pH may range from about5.5 to about 10, preferably from about 6.5 to about 9, depending on themetal used. Preferably, the pH of the solution is adjusted by theintroduction and removal of CO₂ from the reaction vessel.

One of the advantages of the inventive methods is that BMC may beobtained from metal-containing solutions using less energy relative toknown methods. While the methods may be carried out at any suitabletemperature, e.g., from about 5° C. to the boiling point of thesolution, it is desirable that a limited amount or no heat need be addedto the solution during the formation of the BMC. For example, themethods desirably contemplate maintaining the temperature of thesolution from about 5° C. to about 100° C., more desirably from about15° C. to about 80° C., and even more desirably from about 20° C. toabout 60° C. Preferably, the temperature of the solution may range fromabout 25° C. to about 40° C.

The preparation of various metal carbonates optimally require differentpH and chemical concentrations. For example, the most preferred pH rangefor zinc carbonate is 7.5 to 9, while for silver and nickel carbonatethe most preferred pH range is 6.5-8.0. The most preferred molar ratioof amine to metal is about 5:1 to about 7:1 for zinc and nickel, whilefor silver, the most preferred ratio is about 1:1 to about 3:1.

While the preparation of BMC may be carried out while the reactionvessel is at ambient pressure, it may be desirable to increase thepressure in the reaction vessel in order to increase the yield per literof feed solution. If desired, the pressure in the reaction vessel maydesirably range from about 0 psig to about 1500 psig, more desirablyrange from about 20 psig to about 500 psig, and preferably range fromabout 80 psig to about 250 psig.

In another aspect, the inventive methods provide for a continuous methodof preparing basic metal carbonates selected from the group consistingof zinc carbonate, nickel carbonate, silver carbonate, tin carbonate,lead carbonate, manganese carbonate. lithium carbonate, sodiumcarbonate, and potassium carbonate from metals comprising: (a) providingan aqueous solution of ionized metal, the aqueous solution comprising anionized metal, an amine, carbonic acid, and water in a reaction vessel;(b) adjusting the pH of the solution until basic metal carbonate isformed; (c) recovering the basic metal carbonate from the aqueoussolution by subjecting the aqueous solution to filtration; (d)transferring the aqueous solution which remains after the recovery ofbasic metal carbonate in step (c) into a second vessel; (e) removingcarbon dioxide from the aqueous solution which remains after therecovery of basic metal carbonate in step (c); (f) introducing ametal-containing material into the aqueous solution which remains afterthe removal of carbon dioxide in step (e); (g) oxidizing themetal-containing material to provide a replenished ionized metalsolution; and (h) introducing the replenished ionized metal solutioninto the reaction vessel.

The aforesaid metal solution includes a relatively low concentration ofmetal therein, as it is preferably the solvent system that remains aftera metal solution having a relatively high metal concentration has beenprocessed in accordance with the methods described herein to provideBMC. The depleted metal solution is replenished by the addition of rawmaterial (metal), and the addition of ammonia, carbonic acid, water andoxygen, as needed. The ammonia, carbonic acid and water would beadjusted to the needed levels, and then the metal would be introduced tothe solution. If needed, oxygen would be added during the metal/leachprocess.

In a related aspect, the inventive methods provide for the preparationof basic zinc carbonate (BZC) by the introduction of a zincmetal-containing material into a solution of ionized zinc, the solutioncomprising zinc, an amine, carbonic acid, and water. Illustrative ofsuitable zinc materials are zinc metal, bronze, zinc-containingplastics, alloys, compounds, and clads.

Desirably, and prior to introduction into the reaction vessel, the zincmetal-containing material is dissolved in a zinc-depleted solvent systemcomprising an amine to provide a solution which contains a relativelyhigh concentration of zinc, which is preferably at least 15 g/L, morepreferably at least 20 g/L, and most preferably at least 30 g/L zinc(II). Desirably, the ammonia concentration ranges from about 60 g/L toabout 96 g/L, and the primary reaction vessel is at about 50 psig toabout 300 psig, wherein this zinc-replenished solution is thenintroduced into the primary reaction vessel wherein BZC is formed.

Desirably, the methods of the invention contemplate that, in thereaction vessel, the molar ratio of ammonia to zinc ranges from about3:1 to about 8:1; the pH of the solution in the reaction vessel rangesfrom about 7 to about 10; the temperature of the solution in thereaction vessel ranges from about 5° C. to about 80° C.; and thepressure in the reaction vessel ranges from about 0 psig to about 1500psig. More desirably, in the reaction vessel, the molar ratio of ammoniato zinc in the solution ranges from about 4:1 to about 7:1; the pH ofthe solution in the reaction vessel ranges from about 7 to about 9; thetemperature of the solution in the reaction vessel ranges from about 20°C. to about 60° C.; and the pressure in the reaction vessel ranges fromabout 20 psig to about 500 psig. Preferably, in the reaction vessel, themolar ratio of ammonia to zinc ranges from about 5:1 to about 7:1; thepH of the solution in the reaction vessel ranges from about 7.5 to about9; the temperature of the solution in the reaction vessel ranges fromabout 25° C. to about 40° C.; and the pressure in the reaction vesselranges from about 80 psig to about 250 psig.

In another aspect of the invention, the inventive methods provide forthe preparation of BNC by the introduction of a nickel metal-containingmaterial into a solution of nickel, the solution comprising nickel, anamine, carbonic acid, and water, wherein the solution comprises a molarratio of ammonia to nickel ranging from about 5:1 to about 7:1, the pHof the solution in the reaction vessel ranges from about 6.5 to about8.0, the temperature of the solution in the reaction vessel ranges fromabout 25° C. to about 60° C., and the pressure in the reaction vesselranges from about 0 psig to about 150 psig.

In another aspect of the invention, the inventive methods provide forthe preparation of BSC by the introduction of a silver metal-containingmaterial into a solution of silver, the solution comprising silver, anamine, carbonic acid, and water, wherein the solution comprises a molarratio of ammonia to silver ranging from about 1:1 to about 3:1, the pHof the solution in the reaction vessel ranges from about 6.5 to about8.0, the temperature of the solution in the reaction vessel ranges fromabout 25° C. to about 60° C., and the pressure in the reaction vesselranges from about 0 psig to about 150 psig.

As mentioned previously, an aspect of the inventive methods desirablyprovides a means for the continuous preparation of BMC. FIG. 1 is aschematic diagram which provides an exemplary operational flow of amethod of providing BMC in accordance with this aspect of the invention.Referring to this figure, the method includes processing stages that maybe referred to as precipitation 1, filtration 3, CO₂ separation 5, andleaching 7. In the precipitation process, BMC is formed and precipitatedfrom an aqueous solution comprising metal, ammonia, and carbonic acid(provided via the introduction of CO₂ 2, as described herein), asdescribed in more detail herein. After BMC formation is completed, thesolution may be filtered 3 to recover the BMC 4.

The filtration process contemplated by the invention may be performed byany suitable means, but is desirably performed under pressure (e.g.,between about 1 psig and about 1500 psig) to prevent desorption of CO₂,the latter potentially causing solids to re-dissolve in the solventsolution. Further, filtration under pressure (above ambient) may preventthe solids from agglomerating at the bottom of the filter.

After filtration is completed, the metal-depleted solvent desirably maybe degassed to remove excess CO₂ by boiling for a designated time in avessel equipped with a condenser (to collect the distillate).Alternatively, or in addition, CO₂ may be removed by air stripping orpressure reduction. The CO₂ removed by degassing may be reused byrecycling 6 it back to the precipitation vessel 1. The metal-depletedsolvent may then be used in a leaching/oxidation process 7 to obtain areplenished metal solution, which solution then may be recycled andutilized in the method described herein (to provide BMC). As this methodprovides for continuous processing in a closed loop, waste production isminimized and lower energy consumption is achieved.

The exemplary continuous processing illustrated in FIG. 1 is provided asone possible embodiment of the inventive method, and may be modified asdesired. For example, the replenished metal solution may be diluted withwater prior to its use in the method in order to restore an appropriatesolution concentration. Also, after BMC is formed, and prior tofiltration, the resultant slurry may be subjected to a thickeningprocess.

The inventive method also contemplates preparing BMC by contacting metalwith an aqueous solution comprising an amine, carbonic acid (which maybe present as a carbonate, as described herein), and oxygen underconditions where the metal is converted into BMC; and recovering theBMC.

The invention further contemplates a method of forming BMC comprisingthe steps of providing metal hydroxide in an aqueous solution comprisingan amine and a sufficient amount of carbonic acid. Those skilled in theart will appreciate that metal hydroxide may be formed when the solutionhas a high concentration of hydroxide ions relative to carbonate ions,and that the metal hydroxide is disassociated in the presence of water,providing zinc ions in the aqueous solution.

It is also within normal reason to expect that the carbonate anion couldbe replaced with other anions, including nitrates, sulfates, andphosphates.

The following examples further illustrate the invention but, of course,should not be construed as in any way limiting its scope.

Example 1

This example demonstrates production of BZC by reducing the pH of asolution containing zinc, ammonia and CO₂.

1.5 L of an aqueous solution containing CO₂, 76 g/L NH₃, 91 g/L zincoxide, and at a pH of 10.5, were added to a 2 L pressure reactor. Thereaction was started at room temperature. CO₂ gas was added to thesolution until a pressure of 100 psi was obtained. The CO₂ was bubbledinto the solution at a rate of 0.1 LPM, with constant mixing. At 0.75hours, the pH was 8.7, the temperature had risen to 36° C. and thepressure had dropped to 70 psi. After 1.25 hours, the reaction wasstopped, and filtered; 140 g of white solids were collected byfiltration. The remaining solution had a pH of 8.7, a temperature of 34°C., and contained CO₂ and 65 g/L NH₃. The collected solids constituted50.3% zinc determined by ICP.

This example illustrates the preparation of BZC from a zinc solution bylowering the pH, and without additional energy input (e.g., the solutionwas not heated after introduction into the reaction flask).

Example 2

This example demonstrates production of basic nickel carbonate (BNC) atatmospheric pressure by reducing the pH of a solution containing nickel,ammonia and CO₂.

44 g of nickel metal was added to 0.5 L of an aqueous solutioncontaining 153 g/L NH₃ and 102 g/L CO₂. Air was sparged into thesolution for 4 hours. After 2 hours, nickel leaching was sped up byheating the solution to 60° C. for 2 hours. The solution then wasallowed to mix overnight. CO₂ was bubbled into the 0.5 L solution at arate of 0.9 LPM at 28° C. At 0.5 hours, green solids were seen. CO₂addition was continued for 1 hour more and then the solution wasfiltered. 10 g of green solids were recovered. EDS analysis showed thepresence of nickel, carbon and oxygen only.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any nonclaimed element as essential to the practice of theinvention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

1. A continuous method of preparing basic metal carbonates selected fromthe group consisting of zinc carbonate, nickel carbonate, silvercarbonate, cobalt carbonate, tin carbonate, lead carbonate, manganesecarbonate, lithium carbonate, sodium carbonate, and potassium carbonatefrom metals comprising: (a) providing an aqueous solution of ionizedmetal, the aqueous solution comprising an ionized metal, an amine,carbonic acid, and water in a reaction vessel; (b) adjusting the pH ofthe solution until basic metal carbonate is formed; (c) recovering thebasic metal carbonate from the aqueous solution by subjecting theaqueous solution to filtration; (d) transferring the aqueous solutionwhich remains after the recovery of basic metal carbonate in step (c)into a second vessel; (e) removing carbon dioxide from the aqueoussolution which remains after the recovery of basic metal carbonate instep (c); (f) introducing a metal-containing material into the aqueoussolution which remains after the removal of carbon dioxide in step (e);(g) oxidizing the metal-containing material to provide a replenishedionized metal solution; and (h) introducing the replenished ionizedmetal solution into the reaction vessel.
 2. The continuous method ofclaim 1, wherein the amine is ammonium hydroxide.
 3. The continuousmethod of claim 1, wherein the temperature of the solution ranges fromabout 5° C. to about 100° C.
 4. The continuous method of claim 1,wherein the temperature of the solution is from about 15° C. to about80° C.
 5. The continuous method of claim 1, wherein reaction vessel is aspray chamber, a stirred tank reactor, a rotating tube reactor, or apipeline reactor.
 6. The continuous method of claim 1, wherein the pH isadjusted by increasing or decreasing the CO₂ concentration.
 7. Thecontinuous method according to claim 1, wherein step (b) is carried outat ambient pressure.
 8. The continuous method of claim 1, wherein thepressure in the reaction vessel during step (b) ranges from about 0 psigto about 1500 psig.
 9. The continuous method of claim 8, wherein thepressure in the reaction vessel during step (b) ranges from about 20psig to about 500 psig.
 10. The continuous method of claim 9, whereinthe pressure in the reaction vessel during step (b) ranges from about 80psig to about 250 psig.
 11. The continuous method of claim 1, whereinthe metal-containing material is selected from the group consisting ofmetal-containing plastics, alloys, clads, or compounds.
 12. Thecontinuous method of claim 1, wherein the metal is zinc.
 13. Thecontinuous method according to claim 12, wherein the ionized metal iszinc, and wherein during step (b) the molar ratio of ammonia to ionizedmetal in the reaction vessel ranges from about 3:1 to about 8:1, the pHof the solution in the reaction vessel ranges from about 7 to about 10,the temperature of the solution in the reaction vessel ranges from about5° C. to about 80° C., and the pressure in the reaction vessel rangesfrom about 0 psig to about 1500 psig.
 14. The continuous methodaccording to claim 13, wherein during step (b) the molar ratio ofammonia to ionized metal in the reaction vessel ranges from about 4:1 toabout 7:1, the pH of the solution in the reaction vessel ranges fromabout 7 to about 9, the temperature of the solution in the reactionvessel ranges from about 20° C. to about 60° C., and the pressure in thereaction vessel ranges from about 20 psig to about 500 psig.
 15. Thecontinuous method according to claim 14, wherein during step (b) themolar ratio of ammonia to ionized metal in the reaction vessel rangesfrom about 5:1 to about 7:1, the pH of the solution in the reactionvessel ranges from about 7.5 to about 9, the temperature of the solutionin the reaction vessel ranges from about 25° C. to about 40° C., and thepressure in the reaction vessel ranges from about 80 psig to about 250psig.
 16. The continuous method according to claim 1, wherein theionized metal is nickel, and wherein during step (b) the molar ratio ofammonia to ionized metal in the reaction vessel ranges from about 5:1 toabout 7:1, the pH of the solution in the reaction vessel ranges fromabout 6.5 to about 8.0, the temperature of the solution in the reactionvessel ranges from about 25° C. to about 60° C., and the pressure in thereaction vessel ranges from about 0 psig to about 150 psig.
 17. Thecontinuous method according to claim 1, wherein the ionized metal issilver, and wherein during step (b) the molar ratio of ammonia toionized metal in the reaction vessel ranges from about 1:1 to about 3:1,the pH of the solution in the reaction vessel ranges from about 6.5 toabout 8.0, the temperature of the solution in the reaction vessel rangesfrom about 25° C. to about 60° C., and the pressure in the reactionvessel ranges from about 0 psig to about 150 psig.
 18. The methodaccording to claim 1, further comprising the step of introducing carbondioxide removed in step (e) into the reaction vessel.
 19. The methodaccording to claim 1, wherein transfer step (d) occurs prior to theremoval of carbon dioxide step (e).
 20. A method of preparing BMCselected from the group consisting of zinc carbonate, nickel carbonate,silver carbonate, cobalt carbonate, tin carbonate, lead carbonate,manganese carbonate, lithium carbonate, sodium carbonate, and potassiumcarbonate from metals comprising: contacting the metal with an aqueoussolution comprising an amine, carbonic acid, and oxygen under conditionswhere the metal is converted into basic metal carbonate; and recoveringthe basic metal carbonate, wherein the metal is selected from the groupconsisting of zinc, nickel, silver, cobalt, tin, lead, manganese,lithium, sodium, and potassium.
 21. A method of forming basic zinccarbonate comprising: contacting zinc with an aqueous solutioncomprising an amine, carbonic acid, and oxygen under conditions wherethe zinc is converted into basic zinc carbonate; and recovering thebasic zinc carbonate.
 22. A method of forming basic zinc carbonatecomprising: contacting zinc with an aqueous solution comprising anamine, carbonic acid, and oxygen under conditions where the zinc isconverted into basic zinc carbonate; and recovering the basic zinccarbonate, wherein the aqueous solution comprises a molar ratio of amineto zinc from about 3:1 to about 8:1, the pH of the solution ranges fromabout 7 to about 10, the temperature of the solution in ranges fromabout 5° C. to about 80° C., and the pressure ranges from about 0 psigto about 1500 psig.
 23. A method of forming basic zinc carbonatecomprising: contacting zinc with an aqueous solution comprising anamine, carbonic acid, and oxygen under conditions where the zinc isconverted into basic zinc carbonate; and recovering the basic zinccarbonate, wherein the aqueous solution comprises a molar ratio of amineto zinc from about 4:1 to about 7:1, the pH of the solution in thereaction vessel ranges from about 7 to about 9, the temperature of thesolution in the reaction vessel ranges from about 20° C. to about 60°C., and the pressure in the reaction vessel ranges from about 20 psig toabout 500 psig.
 24. A method of forming basic zinc carbonate comprising:contacting zinc with an aqueous solution comprising an amine, carbonicacid, and oxygen under conditions where the zinc is converted into basiczinc carbonate; and recovering the basic zinc carbonate, wherein theaqueous solution comprises a molar ratio of amine to zinc from about 5:1to about 7:1, the pH of the solution in the reaction vessel ranges fromabout 7.5 to about 9, the temperature of the solution in the reactionvessel ranges from about 25° C. to about 40° C., and the pressure in thereaction vessel ranges from about 80 psig to about 250 psig.
 25. Amethod of forming basic nickel carbonate comprising: contacting silverwith an aqueous solution comprising an amine, carbonic acid, and oxygenunder conditions where the silver is converted into basic silvercarbonate; and recovering the basic silver carbonate.
 26. A method offorming basic silver carbonate comprising: contacting nickel with anaqueous solution comprising an amine, carbonic acid, and oxygen underconditions where the nickel is converted into basic nickel carbonate;and recovering the basic nickel carbonate.